lead reactive Jack Russel

JR's have a mind of their own onaclearday It's difficult to change learned behaviour.
Try positive reinforcement when you have visitors, ignore the bad behaviour and praise her when she does what you want. Enlist the help of a friend to come calling until your dog gets the hang of things.
The lead thing is tricky, if you become anxious when another dog approaches this will transmit to your JR. Try to be more relaxed, turn and go in the opposite direction to the other dog so she learns lunging won't get her anywhere. There is no easy answer especially with an eight year old dog who has had major life changes. Love her and praise her when she is good,

JRs Certainly are a force to themselves we have had 2 and both where very head strong little dogs.
When out on walks we always kept Barney (now deceased) on a short lead much easier to control,I hate extending leads anyway this always worked for us.
When she gets excited towards visitors just gently remove her to the sitting position and keep doing so until she gets the message she will eventually just may take longer due to her age and bad habits already learnt. Good luck x

One of JRs gets over excited when we have visitors. I always ask them to ignore her and not even make eye contact until she calms down. She doesn't jump up, just barks for a minute or two, which can seem like a very long time when you want her to shut up.

They lunge when they're on a lead because they know they can't escape and being JRs they like to get in first! I don't like extending leads either.

I would ask your relative if she has always been lead reactive and if there was a trigger. Background information is always useful when tackling behavioural problems.
I would then find a good training class near you. Ask around your area for recommendations, since taking her to someone who does not use positive reinforcement training could set her back and escalate the problem.
As with any training, it takes time, but so worth it when you see the improvement.

Take her to doggy training classes. I agree with petnanny

In our Bronze Class we had a reactive JR (and a reactive Lurcher and a reactive Heinz) by the end of the 8 weeks they were a lot calmer.

One thing our behaviourist showed us when Sam was excitable when visitors arrived was to shut Sam in his cage for 10 mins or so and then let him out.

He was a different dog . That 10 mins allows your dogs very sensitive nose to take on board all the nice smells so when he is let out its all very matter of fact.

Tell your guests at that stage to ignore your dog unless it has all 4 paws on the floor to reinforce good behaviour.

I cant help with the lead problem I'm afraid but a local dog centre here does classes in training reactive dogs. Maybe there is something near to you .

Firstly I'd use a harness rather than attach the lead to the collar.
Then every time he/she meets another dog and kicks off turn swiftly around and walk in the opposite direction.
Practice, practice, practice.
Reward with something tasty every time there is no aggro.

I agree with flex about the harness too. You can get some with a ring on the chest part and another ring on the back. You then buy a lead with a clip at both ends so you have control of two parts of the dog and the ‘pull’ is towards you walking at the side.

Best dog training harnesses